1. Field of the Invention
Example embodiments generally relate to an image reader and an image forming apparatus, and more particularly, to an image reader for reading an image on an original document sheet and an image forming apparatus including the image reader, for example.
2. Description of the Related Art
Related-art image forming apparatuses, such as copiers, facsimile machines, image scanners, or multifunction printers having at least one of copying, printing, scanning, and facsimile functions, typically form an image on a recording medium (e.g., a sheet) according to image data using electrophotography. Thus, for example, an image reader reads an image on an original document sheet to generate image data; a charger uniformly charges a surface of an image carrier; an optical writer emits a light beam onto the charged surface of the image carrier to form an electrostatic latent image on the image carrier according to the image data; a development device supplies toner particles to the electrostatic latent image formed on the image carrier to make the electrostatic latent image visible as a toner image; the toner image is directly transferred from the image carrier onto a sheet or is indirectly transferred from the image carrier onto a sheet via an intermediate transfer member; a cleaner then cleans the surface of the image carrier after the toner image is transferred from the image carrier onto the sheet; finally, a fixing device applies heat and pressure to the sheet bearing the toner image to fix the toner image on the sheet, thus forming the image on the sheet.
In such image forming apparatuses, the image reader may include a lighting device in which a light-emitting diode (LED) is used as a light source to provide quick warm-up, energy saving, and a long life of the light source.
However, the LED has a small light-emitting surface, roughly equivalent to a point source, and therefore does not provide uniform illuminance distribution in a sub-scanning direction. To address this problem, the lighting device may include a guide member for guiding light emitted by the LED.
Thus, for example, one related-art image reader includes a lighting device including a board, a plurality of light sources provided on the board, and a plastic guide member for guiding light emitted by the plurality of light sources. The guide member has a box shape and includes an incident face for receiving light emitted by the plurality of light sources, an emission face for emitting the light, and a reflecting face connecting the incident face to the emission face to reflect the light. Light entering the guide member travels from the incident face to the emission face directly or is reflected by the reflecting face before reaching the emission face.
Accordingly, when light emitted by the plurality of light sources passes through the guide member, the guide member gives the light uniform illuminance distribution, so that the light is output from the emission face to an original document sheet having the uniform illuminance distribution. After the light is reflected by the original document sheet, the light is again reflected by a reflection mirror and enters an image forming lens. The image forming lens forms an image in a CCD (charge coupled device), and the CCD reads the image.
However, such image reader does not optically shield the reflection mirror, the image forming lens, and the CCD from the plurality of light sources. Accordingly, flare light generates and the CCD may not read a bright image.
To address this problem, another related-art image reader includes a frame for shielding a reflection mirror from a light source to reduce flare light. The image reader further includes a lighting device in which the light source and a planar reflector for reflecting light emitted by the light source toward an original document sheet are attached to a holder plate. In order to position the light source with respect to the reflector to generate uniform illuminance distribution in a sub-scanning direction on an original document sheet, the lighting device and a reading device, which includes a reflection mirror, an image forming lens, and a CCD, serve as separate units, respectively, and the lighting device is attached to the frame after adjusting a position of the light source with respect to the reflector.
In other words, the lighting device is positioned with respect to the reading device manually, and therefore it is difficult to position a peak amount of light in the illuminance distribution in the sub-scanning direction at the center of the CCD for reading an image. As a result, the CCD may not read a bright image.